1. Technical Field
The present invention related to a method for surface treatment and a method for forming fine wiring.
2. Description of the Related Art
Methods for forming fine wirings in related art are etching resist method and laser method. The etching resist method includes coating on a substrate, pre-coated with a resist which is a conductive layer with a, photosensitive material; exposing and developing a circuit pattern; and etching the conductive layer according to the resist pattern to form a wiring. However, the etching resist method requires large scale facilities and complicate processings, has only several tens of percentages of efficiency in use of materials of which most are thus wastes, increases manufacturing costs, requires forming and removing a resist layer, and eventually does not form a sufficient fine wiring.
The laser method includes forming a water repellent layer on a substrate; removing a part of the water repellent layer by laser light; and spraying conductive ink to the part where the water repellent layer is removed to form a conductive wiring. However, this method increases manufacturing costs and is complicate and inefficient due to additional use of a laser light generating device and additional forming and removing steps of the water repellent layer.
Accordingly, an inkjet method is recently introduced for forming a fine wiring on a substrate which has several advantages including a selective formation of fine wirings. A method, including coating a substrate with a liquid, in which conductive fine particles are dispersed, by an ink-jet method and forming a conductive pattern by the heat-treatment or the laser exposure, has been recently introduced. This method reduces significantly manufacturing processes and amount of materials to be used since the photolithography is not any more required.
However, until now it still has problems such as spreading of ink droplets and deterioration of the interface adhesion between a droplet and a substrate. A degree of spreading of ink droplets is depending on a diameter of the droplet ejected from an ink-jet head nozzle, the surface tension of ink and the surface energy of a substrate. There is a limitation to reduce a size of the head nozzle of an ink-jet and spreading of ink droplets since a certain amount of metal nanoparticles is contained in the ink to form a conductive wiring. Further a material used for preventing the spreading of ink droplets has low surface energy and thus is not mixed well with other compounds. When the surface of a substrate is treated for preventing the spreading of droplets, it deteriorates the interface adhesion. On the other hand, when the surface treatment is performed for improving the interface adhesion, it increases the spreading of ink droplets.
Therefore, a great deal of development researches is currently under way on methods for improving the interface adhesion with a substrate and forming finer wirings which are highly demanded for the smaller, lighter, and thinner electric components.